In some cases, a projector for projecting images cannot be placed at the front center of a object on which the images are projected such as a screen for the reason of layout of the room where the projector is installed or for other reasons. In such cases, the projector is shifted either to the left or to the right to project images in an oblique direction. However, this arrangement produces a phenomenon of distorting projected images in trapezoidal shape according to the angle of the projector placed in this manner (trapezoidal distortion). When a projector provided with a pair of left and right speakers is shifted from the front center of the screen, an observer positioned at the front center of the screen cannot receive sounds with appropriate sound volume balance of the left and right speakers.
Japanese Patent Publication No. 2004-163453 proposes a projector which has function of correcting trapezoidal distortion by projecting images distorted in the opposite direction beforehand and which is capable of controlling left-right sound balance according to the level of correction for the trapezoidal distortion, that is, installation angles of the projector. According to the projector disclosed in Japanese Patent Publication No. 2004-163453, images and sounds can be provided with no trapezoidal distortion and with appropriate sound volume balance even when the projector cannot be placed at the front center of the screen.
According to the projector of the type which corrects trapezoidal distortion by distorting images in the opposite direction before projection as the projector shown in Japanese Patent Publication No. 2004-163453, distortion of images is achieved by removing apart of pixels constituting images. In this case, images formed by a smaller number of pixels than that of normal images are produced, which lowers the image quality (resolution) of the projected images.